This invention relates to a device for adjusting the position of the tube through which a carrier strand passes before being coated with molten polymer in one operation in the production of a composite yarn. The tube acts as the male die and the polymer extrusion orifice functions as a female die; together the dies define an annular space through which the coating polymer passes.
Two variables which can be controlled during application of the coating polymer to the carrier strand in production of a composite yarn are carrier strand velocity, and melted polymer extrusion rate or quantity of resin extruded per unit time. The velocity, however, of the polymer being applied to the carrier strand is not entirely a function of the extrusion rate, but is also affected by the area of the annular space between the carrier tube and the extrusion orifice.
During operation of a machine, in producing a variety of composite yarns, a severe problem became evident. During apparently satisfactory operation, the molten polymer being applied to coat the moving carrier strand would suddenly fail to adhere to the strand. Apparently the velocity of the molten polymer being applied, compared to the velocity of the carrier strand, was at a critical point, and a slight change in running conditions caused the polymer coating to break loose. The polymer, being extruded continuously, would accumulate at the extrusion orifice. After a short interval of time, the accumulated polymer would break loose and jam the mechanism of the machine. Of course, the accumulation or "slug" of polymer, preceded and followed by bare sections of the carrier strand, interrupted the production of satisfactory quality yarn.
In order to correct this type of misoperation, it has been found to be essential that the velocity of the molten polymer being applied to the carrier strand be controllable. This may be accomplished by adjusting the annular space between the tube through which the carrier strand passes and the polymer extrusion orifice, as by having one end of the carrier tube cone shaped and placed concentrically within a funnel shaped die orifice so that movement of one end of the carrier tube from inside the die toward the strand exit reduces the annular space between the tube and the extrusion orifice. Small vertical movement increments can result in proportionally large annular space changes.